An 18-month-old male is brought to the ED for evaluation of a brief episode of tonic–clonic extremity movements immediately after a spanking in the grocery store. The child reportedly screamed, became limp and pale, fell to the ground, and exhibited the unusual movements. The episode lasted about 1 min and occurred about 30 min before. The toddler is now interactive, appears healthy, and has normal vital signs. What is the MOST likely diagnosis?